An attractive hairstyle is generally regarded today as an indispensable part of a groomed appearance. Based on current fashion trends, hairstyles are regarded time and time again as being chic which can be set up and/or maintained for an extended period up to several days using only setting agents. Hair treatment products that serve to permanently or temporarily shape the hair therefore play an important role. While the chemical structure of the keratin-containing fibers is modified through reduction and oxidation during permanent reshaping, such modifications of the chemical structure do not take place during temporary reshaping. Such products for temporary shaping usually include synthetic polymers and/or waxes as the setting agent.
The most important characteristic of a product for temporarily shaping keratin-containing fibers, hereinafter also called styling product, is that the greatest possible hold is given to the treated fibers in their newly modeled shape—i.e., a shape that is impressed upon the fibers. If the keratin-containing fibers are human hairs, this is also referred to as a strong hairstyle hold or high holding strength of the styling product. The hairstyle hold is determined substantially by the type and quantity of the setting agents used, although the other components of the styling product and the form of application can also have an impact.
The spray application of appropriate cosmetic preparations has great significance in the region of the temporary deformation of keratin-containing fibers, with the preparations generally being applied as pump sprays or aerosol sprays. For this purpose, the cosmetic preparations are packaged in a dispensing device from which they are sprayed through a valve either by means of mechanical force effect or with the aid of a propellant. Both methods have obvious drawbacks. While pump sprays are generally not suitable for the long-lasting uniform spay application of hair-cosmetic preparations, aerosol sprays are based on the use of propellants or propellant gases, which, on the one hand, do not have any cosmetic effect and, on the other hand, pose a danger if handled improperly.
Against this background, a need exists for alternative ways to atomize hair-cosmetic preparations. Flash evaporation has proven its worth as such an alternative spraying method. In this method, which is described in international patent application WO 200183071 A1 (Henkel), for example, a liquid or pasty solvent-containing composition is heated in an enclosed space to a temperature above the boiling point of the solvent, thus producing overpressure in the composition. Upon relaxation (throttling) of the pressure, the liquid vaporizes the liquid and can then be atomized by means of a suitable nozzle, for example.
Therefore, even if flash evaporation is suitable in principle for the spray application of hair-cosmetic preparations, but not every hair-cosmetic preparation can be simultaneously atomized by means of a flash evaporation method. On the one hand, this is due to the heating of the cosmetic preparation required for flash evaporation; on the other hand, it is due to the specifics of the atomized spray produced as a result of flash evaporation, such as the size of the droplets produced and droplet density in the atomized spray.